Apparatus for the production of photographic printing light



Feb. 10, 1942. I GUSCHMlDT ETAL 2,272,646

APPARATUS FOR THE PRODUCTION OF PHOTOGRAPHIC PRINTING LIGHT F'il ed Feb. 1, 1940 2 Sheets-Sheet l qerhard bchmidf w m b a m d n H INVENTORS ATTORNEYS Feb. 10, 1942. 5. SQHMIDT ETAL 2,272,646

' APPARATUS FOR THE PRODUCTION OF PHOTOGRAPHI'C PRINTING LIGHT Filed Feb. 1, 1940 2 Sheets-Sheet 2 5 M g, Gerhard Schmidt J w (O findreaa schimn INVENTOR v ATTORNEY for control or the filters;

Y the diaphragrns and Patented Feb. 10,1942

AT E

cries APPARATUS FOR THE PRODUCTION OF PHOTOGRAPHIC PRINTING LIGHT Gerhard'Schmidt and Andreas Schilling, lDessau,

(Germany, assignors t Corporation, New Delaware 7 General Aniline & Film York, N. 11., a corporation of Application February l, 1940, Serial No. 316,712

In Germany February 2, 31939 1 (Claim.

This invention relates to the production of photographic printing light. For the usual printing apparatus for photographic films, plates, papers etc. a light source is used which emits white or.

- yellow-white light-beams consisting of most of the spectral colors. This light source may be varied by a resistance influencing the brightness of the lamp. The spectral displacement of the light, caused thereby, is irrelevant and depends chiefly on the age of the lamp, and is therefore. not homogeneous and not reproducible. This fact however doesnot matter for the printing of black-white photographic materials.

On account of the progress in color-photography, a printing apparatus isnowadays required in which the color of the printing light is reproducibly variable. The simplest way would be to place filters, for instance graduated filters, in between the printing light and copying material. This method, however, is rather complicated as a printing process itmay happen that each scene has to be printed with a different color filter. Furthermore one could insert color screens between lightsource and film gate, for instance as described in French Patent 818,057, and could cover up the single colors of the screen with a corresponding black screen, so that the remaining colors act as filters. This way, though possible, seems unfavourable, since 1055 of light occurs by partly covering up the filters with black colors and since the possibility exists, that in some way or another an image of the screen is reproduced, thus causing unevenness of the picture. 0

Object ofthis invention, is an apparatus which allows to influence the printing light in an easy way at will and automatically and which warrants an absolute uniformity and maximal light intensity.

In the drawings, which form a part of this appllcation:

Figure 1 is a top. view, partly in section, of one form of apparatus which embodies this invention;

Figure 2 is a detail view of the coupling means Figure 3 is a detail view of thecoupling means for control of t .e diaphragm;

Figure s is a detail View oi means for coupling Figure l, in a light-tight housing {1 a lamp 2 is fixed emitting ra's evenly in all directions; One light beam runs directly 3 and two light beams 4 and E indirectly, each over one mirror 6 and l, which however may be replaced by prisms or similar means. The three light-beams are separated from each other by two walls 8 and 9, so that the single light source 2 supplies in the described way three independent light-beams.

Filters of diiferent colors are inserted in these light-beams. Filter 0 is placed within the lightbeam 3, the second filter H withinth second light-beam t and the third filter l2,within a third light-beam 5. of angular shape, are rotatively mounted round the middle axle Mia, Ha, Ito in such a way, that the light-beams penetrate the filters to a smaller orv larger extent according to their angle of in clination with the light-beams.

The arrangement of these filters is illustrated in details in Figure 2. The arrows 3, 4, 5 represent the light-beams, Nos. Hi, I! and I2 the lilters and Ma, No, there the axles, on which the filters are rotatively mounted.

The filters 10, M, and I2 are mounted on rods and can be rotated through 90 degrees. The rotation is controlled, through suitable connecting rods, by adjusting-knobs 56, ii, E8 on the outside of the housing. These knobs may be turned by hand.

A (see Figure 2), the filter lies completely within the light beam. Thus a relatively large proportion of said beam must pass through the filter. When .the filter is rotated, the knob may be brought into position B, in which filter l2, after it has passed through all intermediate positions,

is in a horizontal position and intercepts substantially none of the light in said beam. Simi- 85 larly, the other two filters i0 and H are also adjustable.

In Figure 1 diaphragms l4, l3, l5 are provided in the path of the light-beams and allow a variation of the intensity of the single light-beams 3, 4, 5. These diaphragms are of such a construction to be shut completely, so that the in tensity varies between zero value and a maximal value depending on the largest possible opening. The operation of these diaphragms is accom plished similarly to the filters it, i i, 12 by knobs 25, 26, 21 placed outside of the housing 5.

Figure 3 illustrates the variable diaphragm" system. The diaphragms i3, i4, M are connected with the adjusting knobs 25, iii, ill by'pins is, w, it and rods it, 2t, it. By litll g these '-'adjusting irnobs the diaphragms ma pletely opened or completely shut through all the intermediate stages.

Sincethe absolute brightness for single light-beams differs with different filterpositions,

The filters, either round or When the adjusting-knob l8 takes up position the exposure time during the printing process should be altered by adjusting it in a suitable manner. This however'is complicated and may be avoided, if filters 10, Ii, 12 and diaphragms 11, l4, I! are coupled with each other. As shown inrigure 4, filters 10, II, and II are connected to control rods 31, It, and It by interconnecting means 43, 44, and 4! respectively. Similarly, diaphragms 18, I4, and II are connected to rods 8!, 31, and I! by means 44, 43, and 45 respectively Here the diaphragm, when the filter is moved tothe horizontal position, narrows down a certain amount depending on the'ihtensity of the filter, and opens again, when the filter is moved towards the upright position. The independent operation of the diaphragms II, i4 it as described above, need not be altered.

The adjustment of brightness necessary as described above, may be accomplished also in another way. An additional graduated filter for instance or a filter graduated in steps (not shown in the drawings) may be placed in front of filter l0, II, it, which is rigidly coupled with the filter in such a way, that it goes into higher grey values, it the filter is in the horizontal position and towards a lower -y-value, ii the filter is moved to the upright position.

By a suitable choice 01' thes grey-filters it is possible, that at any filter position and at a definite position of the diaphragms l3. l4, I! all three light-beams show the same absolute brightness or such a brightness which produces the same photographic effect on the rial.

Figure 1 shows further, that light-beam 3 is thrown directly to, the film gate 18. The two lateral light-beams 4 and I are directed by prisms 29, 80, which may be replaced by mirrors in-such a way, that they are also thrown towards printing matethe film gate iii. The prisms or mirrors may be movably mounted in order to adjust them. The distance between the diaphragms and the film gate must be chosen in such a way, that the film gate is uniformly lighted by all three lightbeams. By such a mixture or different lightbeams,-varlab1e in the described manner as to 'color and intensity, a light of every desired composition may be produced at th light gate, complying with all requirements or the printing process, especially with color material.

The present invention is not limited to three light-beams, but is also applicable to apparatus with only two or more than three light-beams, which in an analogous way are variable as far as color and intensity are concerned.

We claim:

Apparatus for providing printing light which comprises a light source, a printing window, optical means dividing the light emitted by said source into at least two separate beams, additional optical means for directing said beams to said printing window to form a single printing light of controllable spectral composition and intensity. a color filter in the path of at least one of said beams, said filter being adjustable for intercepting any desired proportion of the light rays in the given beam, an adjustable diaphragm in the path 01' each beam which is filtered, and compensating means coupling said diaphragm with its corresponding filter for decreasinlthe portion of said beam transmitted by said diaphragm when said filter intercepts a small proportion of said beam and for increasing the portion of the beam transmitted by the diaphragm when the filter intercepts a larger proportion 01 said beam.

GERHARD SCHMIDT.

ANDREAS SCHILLING. 

